Upgrading 10.13 to Mojave on external clone

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Upgrading 10.13 to Mojave on external clone

My son is running High Sierra (10.13) on his MacBook Air. He still uses a lot of 32-bit apps (Photoshop CS3 and an old copy of Office) for grad school. Today he got an assignment to use an application that requires Mojave. He created a clone using CCC to an external SSD. Since this is a one-time assignment, I was thinking it would be easier to upgrade the clone drive instead of the main internal SSD. First, can that be done? Would he need to change the startup disk in System Preferences to the external drive, then boot to it and run the upgrade? I worry about the reboots that normally happen during an upgrade. Will it stay on the external the whole time? Has anyone done this? Then when he wants to go back to High Siera he just changed the start drive back.

I've read that with Mojave 32 bit apps are supported, but also read the following:

"Another key difference between the two versions is support for 32-bit apps. With Mojave, Apple said they were no longer supporting 32-bit apps without compromise.

So, while a 32-bit app will still run on Mojave, it might act a bit strange. Functionality may be reduced or you may notice the app crashes a lot.

Still, Mojave will run 32-bit apps, unlike Catalina. If you want to keep running 32-bit apps without issue, though, High Sierra is your best bet. It supports 32-bit apps fully."

so that scares me a bit. Any thoughts or suggestions? He needs to work on the project tonight, so if anyone can help quickly, I would really appreciate it.

Thanks!

MacBook Air

Posted on Mar 10, 2021 2:55 PM

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Answer 1

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Limnos

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412,501 points

Mar 10, 2021 5:18 PM in response to Alfredo Jahn2

I attached the drive, formatted it with Disk Utility (though the installer would probably take care of that too) and started the appropriate installer app. I let it run, making the necessary choices when presented with one, and it booted to the new drive at the end. If I wanted to go back to a different system I would option boot. I name my drives according to the system they have on them so it is easy to tell which drive to select when option booting.

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Answer 2

Limnos

Level 10

412,501 points

Mar 10, 2021 3:04 PM in response to Alfredo Jahn2

I was testing different OS versions for a while. I had Mavericks on an internal, El Capitan on another internal, High Sierra on one external drive and Mojave on a flash drive. It worked okay.

You can temporarily start up from another drive by holding down the option key at startup instead of Startup Preferences.

I'd avoid starting iTunes or double clicking on a file to let it choose the app to use. With iTunes it could potentially start the newest version which might make a mess of his library file if he is running an older version under HS. To be safe he should make a backup of everything first.

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Answer 3

Mar 10, 2021 3:58 PM in response to Limnos

You can temporarily start up from another drive by holding down the option key at startup instead of Startup Preferences.

I'd avoid starting iTunes or double clicking on a file to let it choose the app to use. With iTunes it could potentially start the newest version which might make a mess of his library file if he is running an older version under HS. To be safe he should make a backup of everything first.

Thanks. I know that I can hold the option key and restart, but my concern with doing that during the upgrade is that once the computer restarts (I know that upgrades sometimes reboot several times) it might go back to the original startup disk. That would be a disaster. How did you install or upgrade any of your OS drives?

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Answer 4

Mar 10, 2021 6:36 PM in response to Limnos

Cool. My son is upgrading now. Starting with the clone of his High Sierra internal SSD. I had him set the start disk to the external drive. We should know how it works in about 45 minutes. Thanks for all the help. Since he's worried about 32-bit compatibility we decided to upgrade the clone, so we can go back to HS when he completes the project.

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Answer 5

Mar 11, 2021 5:50 AM in response to Alfredo Jahn2

Just to report: The upgrade on the external clone worked perfectly. Took around 45 minutes. He installed the app he needed and all looks good. I told him to try out all his applications to see how Mojave handles them. If all works, I suggested he upgrade his internal drive. Thanks for the help!

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Answer 6

Limnos

Level 10

412,501 points

Mar 11, 2021 9:23 AM in response to Alfredo Jahn2

Great!

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Upgrading 10.13 to Mojave on external clone

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